This study investigates molecular and physical biomarkers of headaches in order to better understand mechanisms of these diseases. There are 3 main parts: 1. Use of capsaicin (active ingredient in hot chili peppers) to trigger release of calcitonin gene related peptide - the hypothesis is that this will be different in headache subjects compared to controls (and if so might be used to predict how these patients will respond to certain medications that modulate calcitonin gene-related peptide). Subjects will be given capsaicin as a cream applied to the forehead or the inner nostril, or a hot sauce that is ingested. 2. Use of capsaicin to trigger eye watering - the hypothesis is that oxygen gas will slow down the amount of eye watering. Cluster headache patients respond very powerfully to oxygen gas but to very little else. The mechanism for oxygen is unknown but in rodents there is data that it works on the parasympathetic / lacrimal gland system. This study translates rodent data into humans in a non-invasive way to confirm the mechanism of this very effective treatment. 3. Use of ice water to trigger headaches - brain freeze causes a very short-lived but intense headache that may cause similar biomarker release as other headache disorders. This may be a useful human model for other headache disorders.